Actinometer



Oct.- 17, 1933. (3,1'- BREWER 1,931,283

ACT INOMETER Filed Jan. .29, 1932 INVENTOR CLARENCE IHREM/ER 1 BY y l ATTORNEY Patented Oct. 17, 1933 UNITED -STATES PA'rizNl*A ori-ICE 1,e31.28s Y l l l Clarence T. Bretergill: Bitner of onethird to Edward W; Menke and one-third to Harry E.Hillstrom, both of Chicago, Ill.

Application January 29, im. serai No. 5119.5364

` 4 claims. (el. azi-z3) An object of this invention is to provide an actinometer, or the like, to measure the intensity of the actinic light emanating from a given subject so that a photographer may be enabled to 5 properly choose the stop opening and shutter timing of his camera to obtain the best results.v

Another object is to provide such an actinometer as will read the timing of the shutter'. directly so that the operator will 'not be required to make additional calculations in order to ob" tain the desired shutter timing, or the stop opening, as the case may be.v That is, he may assume.

a vcertain stop opening, and with this device read the shutter setting directly, or he may assume a certain shutter timing and read the stop opening directly.

Another object is to provide means in conjunction with the above for making theA necessary correction for the light sensitiveness of the plate which Figure 1 is a front elevation of an instrument.

embodying the'invention; a

Fig. 2 is a longitudinal section of the same taken on the line 2-2 of Fig. 1;

Fig. 3 is a partial section and elevation of the Vright-hand'eud of the device showing a modified form of the same;

Figui is a wiring Vdiagram showing how the photoelectric cell is connected into the circuit 140 so as to measure .the intensity of light falling `thereon; and l l Fig. 5' is'a partial section of the photoelectric cell which is exposed to the lightto be measured.

The embodiment illustrated shows an acti- 45 nometer adapted to be held in the hand Aand to be directed toward the object or scene to be photographed so as to measure the intensity lof the actinic lightl received therefrom. Thev acti-v nometer as illustrated comprises a hollow body 50 10 having a shoulder 11 against which is held -a.

photosensitive plate (or photoelectric cell) P which is shown enlarged in Fig. 5, andjwhieh will'later be described in-detail. A glass win- Wr'dow 12Y is secured Ys o'me distance in front of the l photoelectric plate P,.and'is held in place by means of a threaded barrel 13 screwed'in the l' body, and which has a rim 14. If'desired, a ray filter. may be built into this structure, or the de- .vice may be adapted to receive such a lter. This barrel is proportioned to subtend the same angle as .the lens of the cameras with which it is intended to be used.

A cylindrical sleeve 15 is mountedY to rotate on the barrel 10, being heldin place by the rim 14. "AcyIindrical member l'is/mounted to rotate on.the sleeve 15 and carries ascale 1'1 which corresponds to the light senstlveness of the plates .or iilms for use in the camera. This scale is slidable in front ofa markerv on the sleeve 15. so that when the cylindrical member is adjusted on the sleeve for a particular iilm,or plate it will thereafter rotate with itwhen the sleeve is turned. a,

The cylindrical membe'rl carries a scale, 18` which is graduated in terms of either of theusual systems of indicating camera stop openings, such as f. System which is ommnnl'y used on the better types of lens mountings. The cylindrical sleeve 15 is connected by means of ascrew 18 to `an iris diaphragm 19. The scale 16'L shows the position of the iris diaphragm 19 and suitable stops (not shown) are provided to prevent the sleeve 15 being turned beyond the working limits of the diaphragm. Thus it will be seen that by rotating the sleeve, the iris diaphragm may be made to open or close so as to correspond to the stop openings of the lens, and that-these stop openings may be indicated on the graduated scale 16'.

Referring .now to Fig. 5, the photoelectric cell P illustrated comprises a disc V20` of metal, such as steel, aluminum, nickel, molybdenum, timgsten,y copperl silver, etc., of sumcient thickness to be selffsupporting. On one surface is deposited a very thin coating 21, of a suitable light sensitive material, such as selenium, molybdenite, argentite, and the like, whensiiitably prepared. Selenium is preferred, and this is deposited by sputtering, or by painting the disc with red crysV talline selenium dissolved in carbon-disulphide. After either of these treatments. itisplaced in a vacuum furnace andannealedat a-temperature of 150 C.' to 210.'C., dependingon the wave length ofl light-at which it is diIed that the,

cell shall operate. By varying this temperature it can be made more sensitive to the red rays or more sensitive to the violet rays, the crystallization taking place at any temperature between the above limits, provi it is at that temperature a suiiici t-length of A Y v7 5 or a combination of the two.

is exposed to -a source of light, the voltage so.

developed being a function of the intensity of the received light. The above cell `is old and forms no part of the present invention, but it is described as illustrative of the type of cell which is required for the operation of this device. This cell is then connected up in series circuit, as indicated in Fig. 4, the iron plate 20 being connected through a lead 20a to one side of a galvanometer or microammeter G, the other side being connected through a variable resistance R with a metal ring 23 which bears upon the face of the coating 22, which forms the negative side of the cell. The galvanometer, as shown in Fig. 1, may be graduated in terms of the exposure which is expressed in fractios of a second. Thus for a given setting of the adjustable resistance R the galvanometer needle may indicate the length o1' the exposure for a given stop opening.

Referring now to Fig. 2, the resistance R is made up in the form of a coil and preferably .mounted in a block of insulating material 24, which is secured in a knob 25 so as to be rotatable therewith about a screw 25B. One end of this coil is connected through a plate 26V with the lead 27, which in turn is connected to the annular ring 23. The negative side of the galvanometer connects through a lead 28 with a -brush'29 which is suitably mounted so as to be held stationary while the resistance coil R is rotated infront of it, the brush making contact with the coils of the resistance'wire R. If de- 40 sired, the coil may be stationary, and the brush rotatable. Thus by properly choosing the values of the resistance R to correspond to the other resistances of the circuitof Fig. 4, and by properly graduating the scale of the galvanometer, one suchscale as A may represent the shutter setting or timing for a given stop opening as set on the scale 16a. By turning the knob 25 so as to make the total resistances of the circuit a given multiple of that for the setting just describedk posite the indicator is the corresponding stop opening. If the shutter speed desired lies on the vscale B, the knob is first turned to bring the mark B in front of the indicator, after which the sleeve is turned until the needle stands opposite the desired timing on -the scale B. The reading on the scale 16 is the stop opening sought for. The term intensity as used in the specication and claims is intended to cover particularly the intensity of a selected actinic portion of the light measured corresponding to the light to which a given photographic' plate or film is the voltage generated or strength of current 119mm?,

the scale A.` When this is reached the scale 16*- 1s then read, and the reading on this scale op Fig.'3 shows a modification of the device in which the iris diaphragm 19 and its operating parts 15, 16, etc., are omitted and a full stop opening, say f. 2, is used. In this, the housing 10a is provided as before with a rotatable knob 25b which has the same resistance R as Fig. 2. It has a cylindrical member 16"l rotatably mounted thereon which carries on one edge a scale 1'1". graduated to correspond to the light sensitiveness of the hlm and adapted to rotate in front of an indicatoron the knob. This member has another scale -16 on the opposite edge which corresponds to stop openings of the diaphragm. This scale. is movable with the knob in front of two indicators marked A and B (Fig. 3), which correspond to the two scales A, B of the galvanometer.

In operation', the scale 1'1l is first adjusted for film or plate speed, after which the knob 25h is turned to a desired stop opening on the scale 16, let us say on the indicator A. The position of the -pointer is then read on the galvanometer scale A. If this needle runs off the scaleto the right, the knob 25b is ythen turned to some other position where the needle is on the-scale. If the scale 16c is then 'in front of both indicators A and B, then either f. stop'opening so indicated may be used by taking the shutter speed from the corresponding scale of the galvanometer.

In the same way as pointed out before, the shutter speed may be assumed and the knob turned to bring the needle to this speed, after which the stop opening may be read on the corresponding A or B indicator on the scale 16a In this case the adjustment is made by the resistance R, the total amount of light from a given source falling on the photo-sensitive plate P remaining constant.

While I have shown and'described but a few embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made which do not depart from the spirit and scope of ythe invention as disclosed in the appended claims.

1. Anactinometer comprising a housing enclosing a photoelectric cell capable ,o f generating an electrical energy which is a function of tlie intensity of light received froman object to be photographed, adiaphragm adjustable to corre-v spond to various camera stop openings. a galvanometer in series circuit with the cell for measuring the strength of electrical energy generated,V

said galvanometer having a plurality of scales, a resistance in series circuit for varying the position of the galvanometer needle on said scale, each scale having a corresponding indicated position. on the resistance, a member for adjusting saidb resistance, said member and body having cooperating means for indicating each position of' the resistance corresponding to one of said scales,

a sleeve rotatable on the housing and operably connectedto the diaphragm, and a scale on the sleeve adapted'to move in front of a pointer on 140 the housing to indicate the diaphragm opening.

2. An actinometer comprising a housing enclosing a photoelectric cell capable of generating electrical energy which isa function of the in tensity of light received from an object to be photographed, a diaphragm adjustable to correspond to various camera stop openingsVa galvanometer in series circuit with the cell for measuring the strength of the electrical epergy generated, said galvanometer having a scale graduated 15.0

. 1,931,883 in terms of shutter timing, having means for correcting the readings of the galvanometer for the speed of the photographic nlm or plate tobe used, a sleeve rotatable on the housing and operably connected to the diaphragm, and a cylindrical memberrotatably mounted on the sleeve and having graduations corresponding to the speed ot the lm or plate used-and having a scale cooperating with a pointer on the housing to indicate the diaphragm opening.

3. An actinometerJ comprising a cylindrical housing enclosing a photoelectric cell capable of generating electrical energy which is a function of the intensity of light received from an object to be photographed, a diaphragm adjustable by means of a sleeve rotatably mounted on the cylindrical housing to correspond to various camera stop openings, a galvanometer in series circuit with the cell for measuring the strength of the electrical energy generated, and a cylindrical slider rotatably mounted on the sleeve, said slider having a scale corresponding to thestop openings of the diaphragm rotatable in front of an indicator on the housing and having a scale corresponding to illm speed movable in front of an indicator on the sleeve, said galvanometer having a dial located at the side o! said housing,

the axis of the dial being at right anglesto that of the cylindrical housing.

4. An actinometer comprising a cylindrical housing enclosing a photoelectric cell capable ot generating electrical energy which is a function I -of the intensity of light received from an object to be photographed, a diaphragm adjustable by means of a sleeve rotatably' mounted on the cylindrical housing to correspond to various .camera stop openings, a galvanometer in Iseries circuit with the cell for measuring the strength of thev electrical energy generated, a cylindrical slider rotatably mounted on the sleeve, said slider having a scale corresponding to the stop-openings of thediaphragm rotatable in front of an indicator on the housing and having a scale corresponding to nlm speed movable in front of an indicatoren the sleeve, an adjustableresistance in the circuit, and a member rotatably mounted on the housing and having means for varying the adjustable resistance, said galvanometer having a plurality of scales graduated in terms of shutter timing, said member having a plurality o! indicia corresponding to said galvanometer scales and to settings of said resistance so that each indicia indicates one of said scales.

' l CLARENCE T. BREWER.

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